Travis Legleiter, Weed Science Professional Assistant, Department of Botany & Plant Pathology, Purdue University
Common Dandelion is likely the plant species you think of when the term “weed” is mentioned. Almost everybody is familiar with its yellow ray flowers and puffy white seed heads that you no doubt blew on when you were a child. As adults you learn to dislike those yellow flowers and white seed heads as you tirelessly pull and spray them in your yard and flower gardens. Dandelion is not only a weed of residential yards and pastures, but can also become a problem in agricultural fields. This perennial weed is often overshadowed in agronomic fields by pesky summer annuals like pigweeds, lambsquarters, and foxtails; but it can become a major pest itself in long-term no-till fields especially in years like we have had in 2012.
Dandelion is a perennial weed that grows as a rosette and uses a large taproot to overwinter and regrow year after year. Dandelion emerges in both the spring and fall and grows most vigorously in these two seasons of cooler weather. Traditional agronomic practices that included tillage limited the success of dandelion as tillage would bury the small seeds below the soil surface and destroy the taproots; although shifts to long-term no-till has lead to the increased prevalence of the perennial weed. The increased prevalence can also be contributed to earlier growing seasons in which corn residual herbicides are applied earlier and crops are harvested earlier. The lack of residual activity and earlier canopy opening allows for dandelions to flourish in the fall following crop maturity and harvest. This past growing season of drought is likely to also contribute to increased dandelion pressure as corn crops were abandoned, chopped, or harvested early due to poor growing conditions. This in combination with recent fall rainfalls will be very encouraging for dandelions in long-term no till fields.
Control of dandelion in no-till fields starts with a good burndown in the spring along with a residual herbicide for both corn and soybean. This burndown should include 2,4-D with either glyphosate or gramaxone. Gramaxone applied alone will provide an initial quick relief, but plants will rapidly regrow shortly after application. The use of a residual in both corn and soybeans will extend the control of dandelion throughout the growing season. The following products have exhibited the greatest control into the season when applied with a proper burndown in Purdue University research trials:
No-till Corn: Lumax, Fieldmaster, and Bicep II Magnum
No-till Soybean: Sencor, Authority XL, and Valor
Click image to enlarge
Flowering dandelions in no-till corn stubble may become more prevalent following this summers drought conditions.